Abstract Background: The ideal adjuvant treatment of triple negative EBC remains to be defined. CIBOMA/2004-01_GEICAM/2003-11 is a multinational randomized phase III trial exploring adjuvant Cap after the conclusion of conventional chemotherapy in triple-negative EBC patients. Materials and Methods: Patients with operable, node-positive (or node-negative with tumour diameter ≥1 cm), hormone receptor-negative, HER2-negative EBC that have received 6–8 cycles of standard anthracycline and/or taxane-containing chemotherapy in the (neo)adjuvant setting (doxorubicin–cyclophosphamide x 4 allowed for node-negative disease), followed by radiotherapy (if indicated) are eligible. After central confirmation of triple negativity by immunohistochemistry, patients were randomised to either 8 cycles of Cap (1,000 mg/m2 bid, d1–14 q21d) or observation. Stratification factors: centre, prior taxane (yes vs. no), involved nodes (0 vs. 1–3 vs. ≥4) and phenotype (basal vs. non-basal). The primary endpoint is disease-free survival (DFS). Secondary endpoints include 5-year DFS, overall survival and safety. An optional pharmacogenetic sub-study will explore polymorphisms of thymidylate synthase and methylenetetrahydrofolate reductase in relation to efficacy and tolerability of Cap. Present Status: Recruitment of 876 randomized patients was completed in September 2011. Statistical assumptions: expected 30% reduction in the risk of recurrence at 5 years (64.7% to 73.7%, HR 0.701), power of 80% and 0.05 two-sided significance level. Final efficacy analysis will be triggered by 255 events. Baseline characteristics are well balanced and shown in the table below. 75.0% of the patients completed the 8 cycles of adjuvant Cap. Baseline patients characteristics Capecitabine (n = 448)Observation (n = 428)Median Age, years (range)51 (20-79)50 (24-83)Basal Phenotype,%70.772.2Histology,% Ductal87.786.1Lobular1.82.3Other9.811.4Unknown0.70.2Grade,% 13.32.8218.119.0371.969.6Not determinable6.08.4Unknown0.70.2Chemotherapy received,% Adjuvant (only)78.982.2Neoadjuvant (only)15.615.0Adjuvant + Neoadjuvant4.22.6Unknown1.30.2Postmenopausal,%69.267.3Prior Chemotherapy Agents,% Anthracyclines without taxanes32.132.2Anthracyclines and taxanes67.267.6Unknown0.70.2 Conclusions: This randomized phase III adjuvant trial in triple negative EBC patients has completed accrual and event follow up is ongoing. The trial is sponsored by CIBOMA/GEICAM. Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr OT3-1-06.